The invention relates to a fuel pump for an internal combustion engine, with a housing, with at least one piston, with a working chamber that is confined in areas by the piston, with an eccentric shaft or camshaft that acts on the piston, at least indirectly, on its end furthest from the working chamber, and with a prestressing element that loads the piston, at least indirectly, against the eccentric shaft or camshaft.
A fuel pump of this nature is known from the marketplace, as a radial-piston pump, for example. In the case of said fuel pump, a central eccentric shaft is supported in a housing. A cam ring is mounted on an eccentric section of the eccentric shaft. Flat surfaces are formed around the circumference of the cam ring, against which slippers rest. The slippers are interconnected with a cylindrical piston; the end of said cylindrical piston that is furthest from the eccentric shaft confines a working chamber. The piston is loaded by a compression spring against the slipper or against the flat surface of the cam ring.
Three cylinders are provided in the known fuel pump, each comprising one corresponding piston and one corresponding working chamber. When the eccentric shaft moves, the piston is set to moving to and fro, and the fuel present in the working chamber is compressed and ejected via appropriate valve devices, e.g., into a fuel manifold (“rail”) of an internal combustion engine.
In the case of the fuel pump known from the marketplace, the compression spring bears against an end section of the piston that has a markedly greater diameter than the shaft of the piston. The end section and the piston shaft are a single piece and are worked out from a whole unit on a lathe, for example. To guide the compression spring and reduce tension in the transition regions between the piston shaft and the end section, it is necessary to provide grooves and shoulders with different diameters. In combination with the associated great differences in diameter, in particular, this makes costly chip-removal machining necessary, which has a disadvantageous effect on the costs to fabricate the fuel pump.
The object of the present invention, therefore, is to further develop a fuel pump of the type stated initially in such a way that it can be fabricated less expensively.
The object is attained with a fuel pump of the type stated initially by providing a support member that is separate from the piston, which said support member is interconnected with the end region of the piston closest to the eccentric shaft or camshaft, and against which the prestressing element bears.